Systems and methods for providing wireless power to deep implanted devices

ABSTRACT

The present disclosure relates to systems and methods for providing wireless power to implanted devices. Consistent with some embodiments, a power system for providing wireless power to a device implanted in a body of an individual includes a first antenna loop that produces a first electromagnetic wave and at least one second antenna loop that produces a second electromagnetic wave. The first and second electromagnetic waves may interfere with one another to produce an interference pattern including interference maxima. Further, a location of at least one of the interference maxima may be at or substantially close to the device implanted in the body of the individual. A broad distribution pattern at the surface of the skin can reduce the specific absorption rate of the transmission, while focusing the transmission toward the implanted device improves the antenna system&#39;s transfer efficiency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/393,081, filed Sep. 11, 2016, titled “Systems and Methods forProviding Wireless Power to Deep Implanted Devices,” the entirety ofwhich is hereby incorporated by reference.

BACKGROUND

The present disclosure generally relates to wireless power generationsystems and methods. More specifically, and without limitation, thepresent disclosure relates to non-invasive systems and methods forproviding wireless power to an implanted device in an individual orother living being.

Implanted devices, such as devices implanted in the body of anindividual or other living being, may be used for various functions. Forexample, an endoscopic capsule may be implanted to perform telemetrywithin the gastrointestinal tract of a patient. As another example, abrain-computer interface may be implanted to augment and/or repairvarious cognitive and sensory-motor functions. Yet another example is amicro sensor for sensing physiological parameters of an individual.These and other implanted devices may include various subsystems forcollecting data, providing outputs based on collected data, performingcalculations, and/or carrying out various instructions.

Various techniques and systems exist for powering an implanted device.One technique includes providing power to an implanted device throughwireless power transfer using an ex-vivo antenna. This approach has anumber of challenges and shortcomings. One challenge is that theimplanted device may reside deep within the body (e.g., greater than 10mm below the surface of the skin), and therefore wireless power signalsmust travel through multiple layers of body tissue (including layers ofskin, fat, and muscle) before reaching the implanted device. As aresult, wireless power signals become increasingly attenuated as theytravel through successive layers of body tissue, resulting in poor powertransfer efficiency. Another challenge is that the implanted device isnot externally visible, and therefore precise alignment between theex-vivo antenna and the implanted device may be difficult to achieve.This challenge is exacerbated by body movements (e.g., caused byrespiration), which may cause the implanted device to move around withinthe body and/or cause the ex-vivo antenna to be moved from its theinitial placement.

One solution to the transfer efficiency challenge is to simply increasetransmit power of the ex-vivo antenna. While this may be a viablesolution in certain scenarios, it may not be desirable in the context ofthe human body. Indeed, various government and health regulations maylimit the amount of power that can be radiated into the human body.Accordingly, existing systems and methods for providing wireless powerdo not address the challenge of efficiently delivering power toimplanted devices, while minimizing the amount of power radiated intothe human body.

SUMMARY

The present disclosure includes systems and methods for wirelesslyproviding power to implanted devices. In illustrative embodiments, apower system is capable of maximizing the amount of power received at animplanted device, while minimizing the rate at which radiofrequency (RF)energy is absorbed by the body in which the device is implanted.

In accordance with one example embodiment, a power system for providingwireless power to a device implanted in a body of an individual mayinclude a first antenna loop that produces a first electromagnetic waveand at least one second antenna loop that produces a secondelectromagnetic wave. The first and second electromagnetic waves mayinterfere with one another to produce an interference pattern includinginterference maxima. Further, a location of at least one of theinterference maxima may be at or substantially close to the deviceimplanted in the body of the individual.

In accordance with another example embodiment, a method for providingwireless power to a device implanted in a body of an individual mayinclude producing, by a first antenna loop, a first electromagnetic waveand producing, by at least one second antenna loop, a secondelectromagnetic wave. The method may further include interfering thefirst and second electromagnetic waves to produce an interferencepattern including interference maxima. Further, a location of at leastone of the interference maxima may be at or substantially close to thedevice implanted in the body of the individual.

In accordance with yet another example embodiment, a system forproviding power to a device may include a first antenna loop and a powersource configured to provide power to the first antenna loop and causethe first antenna loop to produce a first electromagnetic wave. Thesystem may further include a plurality of second antenna loopsconfigured to absorb a portion of the first electromagnetic wave andproduce second electromagnetic waves. The first and secondelectromagnetic waves may interfere with one another to produceinterference maxima. The system may also include an antenna controllercoupled to the first antenna loop. The antenna controller may beconfigured to control a property of the first antenna loop so as tomaintain the location of at least one of the interference maxima at orsubstantially close to the device implanted in the body of theindividual.

Before explaining example embodiments of the present disclosure indetail, it is to be understood that the disclosure is not limited in itsapplication to the details of construction and to the arrangements ofthe components set forth in the following description or illustrated inthe drawings. The disclosure is capable of embodiments in addition tothose described and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein, as well as in the abstract, are for the purpose ofdescription and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionand features upon which this disclosure is based may readily be utilizedas a basis for designing other structures, methods, and systems forcarrying out the several purposes of the present disclosure.Furthermore, the claims should be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The accompanying drawings, which are incorporated in and constitute partof this specification, and together with the description, illustrate andserve to explain the principles of various exemplary embodiments.

FIG. 1 is a diagram of an example system environment for implementingembodiments consistent the present disclosure.

FIG. 2 is a cross-sectional view of a portion of the example systemenvironment shown in FIG. 1.

FIG. 3 is an illustration of an example antenna system for providingwireless power with a single loop design that lacks beam focusingcharacteristics.

FIGS. 4A and 4B illustrate various performance characteristics of theexample antenna system illustrated in FIG. 3.

FIGS. 5A and 5B illustrate an example embodiment of an antenna systemfor providing wireless power, in accordance with embodiments of thepresent disclosure.

FIGS. 6A, 6B, and 6C illustrate detailed views of example antenna loops,in accordance with embodiments of the present disclosure.

FIGS. 7A and 7B illustrate various performance characteristicsassociated with the example antenna system shown in FIGS. 5A and 5B.

FIGS. 8A and 8B illustrate further characteristics associated with theexample antenna system shown in FIGS. 5A and 5B as a result of theimplanted device being moved and the loading capacitances of thesecondary antenna loops being changed.

FIG. 9 is a flow diagram of an example process for providing wirelesspower to a device implanted in a body of an individual, in accordancewith an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the present disclosure provide improved systems andmethods for providing power to implanted devices. The disclosed systemsand methods are capable of maximizing the amount of power received at animplanted device, while minimizing the rate at which radiofrequency (RF)energy is absorbed by the body in which the device is implanted.Embodiments of the present disclosure are also capable of continuouslyproviding the maximum power to devices implanted at various locationsbelow the surface of the skin, even when the relative position of theimplanted device with respect to the system providing the power changesduring operation.

In accordance with some embodiments, the disclosed systems may includean ex-vivo antenna system capable of radiating power wirelessly to animplanted device. As radiated power travels further into the body, itbecomes more and more attenuated. In order to combat this attenuation,and to maximize the amount of power received at the implanted device,while minimizing the amount of power absorbed by the body, the disclosedantenna system is capable of generating an interference pattern wherebyat least one of the interference maxima (i.e., regions of the highestpower levels) is located at or substantially close to the implanteddevice. In some embodiments, the interference pattern may also begenerated such that the energy is broadly distributed at the surface ofthe skin so as to minimize the peak specific absorption rate (SAR).

The interference pattern may be generated through a combination of, forexample, a primary antenna loop and one or more secondary antenna loops.The primary antenna loop may receive power generated by a power sourceand may radiate the power as electromagnetic waves. The secondaryantenna loops (also referred to as passive radiators) absorb some of thepower radiated by the primary antenna loop and reradiate the absorbedpower also as electromagnetic waves. Alternatively, the secondaryantenna loops may receive power generated by a power source and mayradiate the power as electromagnetic waves. The electromagnetic wavesproduced by the primary antenna loop and the electromagnetic wavesproduced by the secondary antenna loop(s) interfere constructively anddestructively with each other to generate the interference pattern.

Various aspects of the ex-vivo antenna system, including the primaryantenna loop and the secondary antenna loops, may be designed and/orcontrolled during operation, such that at least one of the interferencemaxima is maintained at or substantially close to the implanted device,even when the relative position between the implanted device and theex-vivo antenna system changes during operation. Additionally, oralternatively, various aspects of the ex-vivo antenna system, includingthe primary antenna loop and the secondary antenna loops, may bedesigned and/or controlled during operation, such that the energy isbroadly distributed at the surface of the skin so as to minimize thepeak specific absorption rate (SAR). Accordingly, the ex-vivo antennasystem is capable of forming an interference pattern that broadlydistributes power at the surface of the skin, while providing andmaintaining focused power at or substantially close to the implanteddevice.

Reference will now be made in detail to embodiments according to thepresent disclosure, the examples of which are described herein andillustrated in the accompanying drawings. Wherever possible, the samereference numbers will be used throughout the drawings to refer to thesame or like parts.

FIG. 1 depicts an example system environment 100 for implementingembodiments of the present disclosure. As shown in FIG. 1, systemenvironment 100 includes a number of components. It will be appreciatedfrom this disclosure that the number and arrangement of these componentsis exemplary only and provided for purposes of illustration. Otherarrangements and numbers of components may be utilized without departingfrom the teachings and embodiments of the present disclosure.

As shown in the example embodiment of FIG. 1, system environment 100includes an implanted device 120 and a power system 130. In someembodiments, implanted device 120 is positioned in a subject 110.Subject 110 may be a human subject, an animal subject, or any other typeof living subject. In some embodiments, implanted device 120 may be acentimeter implanted device (i.e., a device having size dimensions atleast one centimeter each), a millimeter implanted device (i.e., adevice having size dimensions less than one centimeter but at least onemillimeter each), or a sub-millimeter implanted device (i.e., a devicehaving size dimensions less than one millimeter each). As illustrated inFIG. 1, implanted device 120 includes an antenna system and a rectifierfor receiving power wirelessly from power system 130 and converting thereceived power to DC for use by subsystems of implanted device 120.Implanted device 120 may be capable of being implanted at variouslocations and at various depths within the body of subject 110. Whileimplanted device 120 is shown in FIG. 1 to be implanted in the arm ofsubject 110, other implant locations are contemplated and theillustrated example is in no way intended to be limiting on the presentdisclosure. Implanted device 120 may move within the body of subject 110after implantation.

Implanted device 120 may include one or more subsystems for performingvarious functions. Examples of an implanted device include a vestibularprosthesis having subsystems for augmenting and/or repairing one or morefunctions of a subject 110's vestibular system, a micro sensor ortelemetry device having subsystems for collecting data about variousbodily systems of subject 110, a brain-computer interface device havingsubsystems for sensing brain activity of subject 110 and converting thesensed signals to instructions for performing various physical actions,a drug delivery device, a neural stimulation device, and a painstimulation device. Other example implanted devices may be used inconjunction with the disclosed embodiments, however, and the enumeratedexamples are in no way intended to be limiting on the scope of thepresent disclosure.

Power system 130 may include one or more ex-vivo antenna systems 132 andone or more power sources 134. Power system 130 may further include oneor more antenna controllers 136. Antenna system 132 may be capable oftransmitting and receiving signals at various radio frequencies usingpower from power source 134. For example, power source 134 may generatepower and provide it to antenna system 132, and antenna system 132 maywirelessly radiate the generated power. Each power source 134 may beimplemented by using any conventional power generation system, such as aportable (e.g., battery operated) or fixed (e.g., a lab power supply)power source, a variable or constant power source, etc. In someembodiments, each antenna system 132 is paired with a single powersource 134. In other embodiments, a power source 134 may provide powerto one or more antenna systems 132, or each antenna system 132 mayreceive power from one or more power sources 134.

Each antenna system 132 may include one or more antenna elements(referred to herein as loops). The design aspects of antenna system 132(e.g., loop location, spacing, size and power, signal frequency, etc.)may be optimized for different implanted devices 120, differentapplications (e.g., different subjects 110), different implantlocations, etc. For example, some antenna systems 132 may be designed tobe held close to the skin of subject 110 (e.g., on the skin of subject110 or a few millimeters away from the skin). Other antenna systems 132may be designed to be held further away. Accordingly, these differencesin location may drive antenna size, loop spacing, signal frequency,etc., subject to constraints of maximizing link gain and minimizingenergy loss in tissue and peak specific absorption rate.

In some embodiments, one or more antenna controllers 136 may beconfigured to adjust, during operation, one or more properties (e.g.,loading capacitances/inductances) of antenna system 132. Additionally,or alternatively, one or more antenna controllers 136 may be designed orconfigured to adjust, during operation, one or more properties (e.g.,frequency, phase, and magnitude) of signal(s) that are fed into antennasystem 132. For example, antenna system 132 may include a tunable phaseshifter that changes the phase of the signals fed into antenna system132.

The adjustments made by antenna controllers 136 may change, duringoperation, the location at which the power is provided by antenna system132. Therefore, in some embodiments, antenna controller 136 may adjustantenna system 132 and/or signal(s) that are fed into antenna system 132to compensate for any misalignment that may have been introduced betweenantenna system 132 and implanted device 120 during operation. Amisalignment between antenna system 132 and implanted device 120 may beintroduced during operation, for example, when implanted device 120moves around within the body of subject 110, and/or when antenna system132 is moved after the initial placement (e.g., due to body movementscaused by respiration). A misalignment between antenna system 132 andimplanted device 120 may also be introduced, for example, when antennasystem 132 is initially misaligned with implanted device 120 (e.g., dueto implanted device 120 not being externally visible). In someembodiments, such a misalignment may be determined based on a signalstrength indicator received from the implanted device 120.

Transmitted signals 150 may include instructions such as, for example,instructions for implanted device 120 to perform telemetry by capturingdata about the environment in which it is implanted. Transmitted signals150 may alternatively, or in addition, include sufficient power forsupplying implanted device 120 with power to run any subsystems includedin implanted device 120. Received signals from implanted device 120 mayinclude data such as, for example, sensed or measured data, stillimages, video, audio, etc. In addition, as indicated below, receivedsignals from implanted device 120 may also include a signal strengthindicator and/or other signals to control the delivery of power to theimplanted device 120.

In some embodiments, implanted device 120 may periodically generate andsend data or signals, such as a received signal strength indicator(RSSI), to antenna controller 136 of power system 130. In suchembodiments, antenna controller 136 may include a control system thatmakes adjustments based on the RSSI information and/or other signalsreceived from implanted device 120. The control system may beimplemented by any suitable combination of hardware, software, and/orfirmware (e.g., a combination of a processor with software orlogic-enabled circuitry). By way of example, a control system of antennacontroller 136 may make be configured to make adjustments to antennasystem 132 and or the signals fed into antenna system 132 such that theRSSI is maximized at implanted device 120.

In embodiments where power system 130 includes a plurality of antennasystems 132, each antenna system may be preconfigured or arranged toinitially provide power to a predetermined regions under the skin ofsubject 110. The predetermined regions may overlap at least partiallywith each other. In such embodiments, one or more antenna controllers136, based on RSSI and/or other signals received from implanted device120, may adjust the plurality of antenna systems 132. The RSSI signalsand adjustments by the antenna controller 136 may be used to determinethe implant location and facilitate alignment between the betweenantenna system 132 and implanted device 120.

Antenna system 132 may transmit and receive data and power using variousnear-field or intermediate-field transmission techniques. Suchtechniques may include non-radiative transmission techniques such asnear/intermediate-field coupling. Examples of near/intermediate-fieldcoupling include inductive coupling and capacitive coupling. In someembodiments, where power system 130 and implanted device 120 communicatevia inductive coupling, antenna system 132 may generate a magneticnear-field to transmit data and/or power to implanted device 120. Insome embodiments, where power system 130 and implanted device 120communicate via capacitive coupling, antenna system 132 may generate anelectric near-field to transmit data and/or power to implanted device120.

FIG. 2 illustrates a cross-sectional view 200 of the example systemenvironment 100 shown in FIG. 1. As shown in cross-sectional view 200,implanted device 120 may be implanted in muscle layer 240 of subject110. Antenna system 132 may transmit power wirelessly to implanteddevice 120 through skin layer 220, fat layer 230, and muscle layer 240of subject 110. Each layer 220-240 of subject 110 may provide varyinglevels of attenuation to the transmissions of antenna system 132.Antenna system 132 may be held close to skin layer 220 of subject 110,leaving an air gap 210 of various distances (e.g., 5-10 mm). Whileantenna system 132 may be held directly against skin layer 220, leavingan air gap 210 between antenna system 132 and skin layer 220 may act asan insulator that helps to minimize tuning defects and stabilizes thetransmission frequency of antenna system 132. While an air gap 210 isused to isolate antenna system 132 from skin layer 220 in the exampleshown in FIG. 2, other electrical insulators may be used. Examples ofelectrical isolators include, glass, ceramic, paper, A.B.S., acrylic,fiberglass, and nylon. In some embodiments, antenna system 132 may bepacked in an insulating material to achieve similar results fromproviding air gap 210.

Since skin layer 220, fat layer 230, and muscle layer 240 are opaque,implanted device 120 may not be externally visible after it is implantedin the body of subject 110. Therefore, accurately aligning antennasystem 132 with implanted device 120 may be difficult, and amisalignment may be introduced between antenna system 132 and implanteddevice 120 during the initial placement of antenna system 132 over theskin of subject 110. Such a misalignment results in inefficient transferof power from antenna system 132 to implanted device 120. A misalignmentbetween antenna system 132 and implanted device 120 may also resultduring operation, for example, because of movement of implanted device120 and/or antenna system 132 away from their initial position(s).

Therefore, consistent with embodiments of the present disclosure,antenna controller 136 may be configured to adjust antenna system 132,during operation, to improve the alignment and location at which thepower is provided by antenna system 132 in relation to implanted device120. Further details on how antenna controller 36 adjusts antenna system132 and corrects misalignments with implanted device 120 are providedherein with reference to example embodiments.

FIG. 3 illustrates an example antenna system 300 with a single antennaloop 310 for providing power to an implanted device. Loop 310 may becircular in shape and may be physically coupled to the surface of oneside of antenna system 300. A power source may provide power to antennasystem 300. Antenna system 300 may provide the power wirelessly to oneor more implanted devices by radiating the power through loop 310. Insome embodiments, loop 310 may be any other closed shape orconfiguration, such as, but not limited to, triangles, rectangles,squares, and hexagons.

FIGS. 4A and 4B are graphical representations of various performancecharacteristics associated with single loop, antenna system 300 of FIG.3. FIG. 4A is a heat map showing a top-down view of the specificabsorption rate and distribution of the RF electromagnetic energyradiated by antenna system 300. The intensity of the heat map representsthe specific absorption rate (SAR), which is the rate at which the RFelectromagnetic energy is absorbed into the human body. As shown in FIG.4A, the power distribution of antenna system 300 is mostly uniformaround loop 310 with the exception of a hotspot at the left side of loop310. Power intensity drops off quickly, however, as it radiates inwardlyand away from loop 310, resulting in poor distribution uniformity in thex-y plane.

FIG. 4B is a heat map showing a cross-sectional view of the SAR anddistribution of electromagnetic energy radiated by single loop, antennasystem 300. As shown in FIG. 4B, the specific absorption rate of antennasystem 300 drops of quickly as the transmitted electromagnetic energyradiates into the body toward implanted device 120. One of the primarycauses of the poor signal penetration of antenna system 300 is a lack ofpower focusing capabilities. A significant amount of power is radiatedaway from the implanted device, thereby resulting in poor power transferefficiency and increased specific absorption rate.

FIGS. 5A and 5B illustrate an example antenna system 500, in accordancewith embodiments of the present disclosure. Antenna system 500 may beused to implement one or more aspects of antenna system 132 of FIG. 1,while addressing one or more of the shortcomings of antenna system 300described above. As shown in FIGS. 5A and 5B, antenna system 500includes a primary antenna loop 510 and one or more secondary antennaloops 530. It will be appreciated from this disclosure that the numberand arrangement of these components is exemplary only and provided forpurposes of illustration. Other arrangements and numbers of componentsmay be utilized without departing from the teachings and embodiments ofthe present disclosure. By way of example, in some embodiments antennasystem 500 may be implemented as a disc-shaped structure having a radiusof approximately 75 mm, as shown in FIG. 5A. Other dimensions andstructures may be implemented, consistent with the teachings of thisdisclosure.

FIG. 5A illustrates a primary side of antenna system 500. Primaryantenna loop 510 includes a matching network 520, and primary antennaloop 510 and/or matching network 520 may be physically coupled to thesurface of the primary side. A power source (e.g., power source 134 ofFIG. 1) may provide power to primary antenna loop 510 through matchingnetwork 520, causing primary antenna loop 510 to produce electromagneticwaves. Matching network 520 may be implemented as a network ofelectrical circuit components (e.g., capacitors, resistors, inductors,etc.) and may be used to match the impedance of antenna system 500 tothe input impedance of the power source at the desired operatingfrequency. Accordingly, the configuration of components included inmatching network 520 may depend on various design characteristics, suchas transmit frequency of antenna system 500, the size and placement ofprimary antenna loop 510 and secondary antenna loops 530, the tissueproperties, the spacing between the loop and the tissue, including anyair gaps and housing material thickness, etc.

FIG. 5B illustrates a secondary side of antenna system 500. In someembodiments, the secondary side may be a side of antenna system 500opposing the primary side. In some embodiments, the secondary side maybe a layer stacked on top of the primary side. As shown in FIG. 5B, oneor more secondary antenna loops 530 may be physically coupled to thesurface of the secondary side. Secondary antenna loops 530 may bepositioned so as to absorb some of the power radiated by primary antennaloop 510 that would otherwise be radiated away from implanted device 120and absorbed by the body of subject 110. Secondary antenna loops 530 mayreradiate the absorbed power as electromagnetic waves.

In some embodiments, one or more secondary antenna loops 530 may eachinclude a matching network (not shown in FIG. 5B) similar to matchingnetwork 520. Further, these secondary antenna loops may be coupled toone or more power sources, providing power to each of the secondaryantenna loops 530 and causing each of them to produce electromagneticwaves.

According to embodiments of the present disclosure, the electromagneticwaves produced by secondary antenna loops 530 and primary antenna loop510 may interfere constructively and destructively with each other togenerate an interference pattern. The generated interference pattern mayinclude regions of interference maxima, where the electromagnetic wavesinterfere constructively, and regions of interference minima, where thewaves interfere destructively.

Various design characteristics of antenna system 500 may affect theinductive and the capacitive coupling properties between secondaryantenna loops 530 and between primary antenna loop 510 and secondaryantenna loops 530, which, in turn, affect the interference patterngenerated by antenna system 500. For example, some designcharacteristics of antenna system 500 may affect the locations and/orintensities of the interference maxima and minima. Accordingly, thedesign characteristics of antenna system 500 may be determined toaccommodate different shapes and sizes of implanted devices 120,different implant depths (and differing levels of attenuation byextension), different locations at which antenna system 500 is intendedto be held (e.g., on the skin, close to the skin, etc.), variations inthe patient's anatomy, including thickness of skin, fat, and muscletissue, as well as to ensure that the power system (e.g., power system130 of FIG. 1) for antenna systems 500 complies with all applicablegovernment and health/safety laws and regulations. The phrase “designcharacteristics” refers to characteristics of antenna system 500 thatare determined prior to the fabrication of antenna system 500, andtherefore cannot be changed during operation.

One design characteristic that affects the coupling properties is thesize of primary antenna loop 510 and secondary antenna loops 530. Forexample, while primary antenna loop 510 and secondary antenna loops 530are shown in FIGS. 5A and 5B to all be the same size, primary antennaloop 510 and one or more secondary antenna loops 530 may be differentsizes and/or one or more secondary antenna loops 530 may be different insize. The number of primary elements 510 and/or secondary antenna loops530 included in antenna system 500 may also be adjusted (e.g., increasedor decreased). Another design characteristic that affects the couplingproperties is the spacing between primary antenna loop 510 and secondaryantenna loops 530 and/or the spacing between secondary antenna loops530. For example, while there is no overlap between primary antenna loop510 and secondary antenna loops 530 in FIGS. 5A and 5B, one or moresecondary antenna loops 530 may overlap each other, one or moresecondary antenna loops 530 and primary antenna loop 510 may overlapeach other, or any combination thereof. A further design characteristicthat affects the coupling properties is the shapes of primary antennaloop 510 and secondary antenna loops 530. For example, primary antennaloop 510 and secondary antenna loops 530 may be hexagonal, square,circular, or any other symmetrical, asymmetrical, or amorphous shapes,or a combination thereof. The orientation of primary antenna loop 510and/or secondary antenna loops 530 may also affect the inductive and thecapacitive coupling properties. For example, while primary antenna loop510 and secondary antenna loops 530 are shown in FIGS. 5A and 5B to beparallel with each other on the x-y plane, any of primary antenna loop510 and secondary antenna loops 530 may be rotated about one or morethree-dimensional axes.

Even when one or a combination of various design characteristics ofantenna system 500 are optimized to maximize the power provided to theinitial implant location of implanted device 120, a misalignment betweenimplanted device 120 and antenna system 500 may be introduced duringoperation. As discussed herein, such a misalignment may causeinefficient transfer of power from antenna system 500 to implanteddevice 120. As further explained below with reference to FIGS. 6A, 6Band 6C, one or more properties of antenna system 500 (e.g., loadingcapacitances/inductances) and/or one or more properties (e.g.,frequency, phase, and magnitude) of the signal(s) that are fed intoantenna system 500 may be adjusted. These adjustments may be made byantenna controller 136 and may cause the locations and/or intensities ofthe interference maxima and minima to change. Therefore, as discussedabove, these adjustments may be used to compensate for the misalignmentintroduced during operation.

Antenna system 500 may be implemented through various configurations andelectromechanical structures. For example, antenna system 500 mayinclude a substrate such as a ridged printed circuit board or a flexiblesubstrate formed to the body shape of a subject 110 wearing antennasystem 500. The size and shape of the substrate may be selectedaccording to one or more design parameters (e.g., the size and depth ofthe implanted device to be powered, the amount of power required by theimplanted device, etc.). Primary antenna loop 510, matching network 520,and secondary antenna loops 530 may be printed thereon. Elements 510-530may be printed using one or more types of ridged and/or flexibleconductive materials such as, for example, copper, gold, silver,aluminum, etc. While primary antenna loop 510 and matching network 520may be printed on the opposite side of the substrate as secondaryantenna loops 530, other configurations are contemplated withoutdeparting from the scope of this disclosure. For example, elements510-530 may be all printed on the same side of the substrate or one ormore secondary antenna loops 530 may be printed on opposing sides of thesubstrate.

In addition, additional layers of antenna loops may be added to antennasystem 500. For example, an antenna system having a substrate withmultiple stacked layers deposited thereon may have a first layerdeposited on the substrate that includes a primary antenna loop 510, asecond layer including one or more secondary antenna loops 530 depositedon top of the primary antenna loop 510 layer, and one or more layers ofadditional secondary antenna loops 530 deposited on top of the firstlayer of secondary antenna loops 530. Each layer of secondary antennaloops 530 may have design characteristics (e.g., size, shape, spacing,and number of secondary antenna loops 530, etc.) similar to, ordifferent from, one or more of the other layers of secondary antennaloops 530.

FIGS. 6A and 6B respectively illustrate detailed views of primaryantenna loop 510 and a secondary antenna loop 530 of antenna array 500shown in FIGS. 5A and 5B. FIG. 6C illustrates both primary loop 510 andsecondary antenna loops 530 of antenna array 500 shown in FIGS. 6A and6B.

As shown in the example embodiments of FIGS. 6A, 6B, and 6C, primaryantenna loop 510 and secondary antenna loop 530 may be implemented ashexagonally-shaped structures. By way of example, each segment of thehexagonal structure may have a length of approximately 25 mm, as shownin FIG. 6A. As will be appreciated, other dimensions and structureshapes may be implemented, consistent with the teachings of thisdisclosure.

In some embodiments, primary antenna loop 510, matching network 520,and/or secondary antenna loop 530 may include one or more loadingcomponents 610. Loading components 610 may include capacitors,inductors, resistors, and/or other electronic circuit components. Thecharacteristics (e.g., capacitance, inductance, etc.) and placement ofloading components 610 may affect the loading capacitances/inductancesof primary antenna loop 510 and secondary antenna loops 530. Further,the loading capacitances/inductances of primary antenna loop 510 andsecondary antenna loops 530 may affect the properties of theelectromagnetic waves (e.g., magnitude and phase) produced by primaryantenna loop 510 and secondary antenna loops 530, which, in turn, affectthe interference pattern. For example, the relative loadingcapacitances/inductances of primary antenna loop 510 and secondaryantenna loops 530 may affect the locations and/or intensities of theinterference maxima and minima of the interference pattern.

In some embodiments, characteristics of one or more loading components610 may be adjustable by antenna controller 136 during operation. Forexample, one or more loading components 610 may be a voltage-controlledvariable capacitor/inductor, and antenna controller 136 may be coupledto, and configured to control, the voltage-controlled variablecapacitor/inductor. Additionally, or alternatively, loading component610 may be, for example, a digitally tunable capacitor or any othervariable reactive element.

Accordingly, in some embodiments, antenna controller 136 may indirectlyadjust the loading capacitance/inductance of an antenna loop duringoperation since the characteristics of the loading components 610determine the loading capacitance/inductance of the antenna loop.Furthermore, antenna controller 136 may also indirectly adjust thelocations and/or intensities of the interference maxima and minima ofthe interference pattern as they are affected by the relative loadingcapacitances/inductances of the primary and secondary antenna loops. Asdiscussed above, these adjustments may be used to compensate formisalignment between implanted device 120 and antenna system 500.

In some embodiments, as shown in FIG. 6C, loading components 610 of oneor more secondary antenna loops 530 may be adjustable during operation,while loading components 610 of primary antenna loop 510 are fixed. Forexample, loading components 610 of secondary loops 530 may be variablecapacitors, while loading components 610 of primary loop 510 may beelements with fixed capacitances. In some embodiments, characteristicsof loading components 610 within a single antenna loop (primary orsecondary) may be the same or substantially the same. For example, asshown in FIG. 6C, loading components 610 of secondary loops 530 may bevariable capacitors that have the same initial capacitance and/orloading components 610 of primary loop 510 may be elements that have thesame, fixed capacitance values.

In some embodiments, loading components 610 of a subset of secondaryantenna loops 530 may be adjustable during operation, while loadingcomponents of the remaining secondary antenna loops 530 are fixed. Insome embodiments, all loading components may be adjustable duringoperation. Further, in some embodiments, a single antenna controller 136may be coupled to and configured to adjust loading components 610 of asingle loop (primary or secondary). Also, in some embodiments, a singleantenna controller 136 may be coupled to and configured to adjustloading components 610 of one or more antenna loops (e.g., the primaryand/or secondary loops).

As discussed above, one or more secondary antenna loops 530 may eachinclude a matching network (not shown in FIG. 5B) similar to matchingnetwork 520. Further, as discussed above, these secondary antenna loopsmay be coupled to one or more power sources, causing each to produceelectromagnetic waves. In such embodiments, power loss from mutualcoupling may be higher compared to embodiments where the secondary loops530 are not powered by power sources.

Consistent with some embodiments of the present disclosure, antennacontroller 136 may be configured to adjust one or more properties of thesignal(s) provided to each of the secondary antenna loops 630. Forexample, antenna controller 136 may be configured to adjust thefrequency, phase, and/or magnitude of the signal provided to each of thesecondary antenna loops 630. Also, in some embodiments, antennacontroller 136 may be a tunable phase shifter.

As will be appreciated from the present disclosure, the frequency,phase, and/or magnitude of the signal fed into primary antenna loop 510and secondary antenna loops 530 affect the properties of theelectromagnetic waves (e.g., the magnitude and phase of such waves)produced by primary antenna loop 510 and secondary antenna loops 530,which, in turn, affect the interference pattern. Therefore, adjustmentsto the frequency, phase, and/or magnitude of the signals fed into theantenna loops may also indirectly change the locations and/orintensities of the interference maxima and minima of the interferencepattern. Accordingly, consistent with some embodiments, antennacontroller 136 may indirectly adjust the locations and/or intensities ofthe interference maxima and minima of the interference pattern as theyare affected by the frequency, phase, and/or magnitude of the signalsfed into the antenna loops.

FIGS. 7A and 7B are graphical representations of various performancecharacteristics associated with antenna system 500 of FIGS. 5A and 5B.In FIGS. 7A-7B, implanted device 120 is directly below primary antennaloop 510. FIG. 7A is a heat map showing a top-down view of the specificabsorption rate and distribution of the RF electromagnetic energyradiated by antenna system 500. FIG. 7B is a heat map showing across-sectional view of the specific absorption rate and distribution ofthe RF electromagnetic energy radiated by antenna system 500. In FIGS.7A and 7B, primary antenna loop 510 has a loading capacitance of 8 pFand all of secondary antenna loops 530 have a loading capacitance of 7.5pF.

As shown in FIGS. 7A and 7B, the power radiated by antenna system 500 isdistributed broadly and uniformly around primary antenna loop 510 andsecondary antenna loops 530 at the surface of the skin of subject 110.Therefore, for a given power transmission level, the power absorbed byhuman tissue per area or per volume (as a measurement of SAR) issignificantly less for antenna system 500's power transmission comparedto antenna system 300. In some embodiments, the maximum SAR caused by atleast one of the first electromagnetic wave or the secondelectromagnetic wave is below or equal to 1.6 watts per kilogram.Moreover, the power provided by antenna system 500, unlike antennasystem 300, is focused at the location of implanted device 120 due tothe constructive interference pattern generated by secondary antennaloops 530. Accordingly, a greater power transfer efficiency to implanteddevice 120 compared to the power transfer efficiency of antenna system300 is achieved while minimizing power loss into the body of subject110.

FIGS. 8A and 8B illustrate further characteristics associated with theexample antenna system shown in FIGS. 5A and 5B as a result of implanteddevice 120 being moved and the loading capacitances of secondary antennaloops 530 being changed. Specifically, in FIGS. 8A and 8B, the loadingcapacitances of secondary antenna loops 530 have been adjusted (e.g.,during operation) such that the location of one of the interferencemaxima is over the new position of implanted device 120. In theillustrations of FIGS. 8A and 8B, the loading capacitance of primaryantenna loop 610 remains unchanged (i.e., 8 pF) from that illustrated inFIGS. 7A and 7B. However, secondary antenna loops 530A-C now have aloading capacitance of 9.0 pF, and secondary antenna loops 530D-F have aloading capacitance of 7.0 pF. In some embodiments, adjustments to theloading capacitances of secondary antenna loops 530A-F may be made byone or more antenna controllers 136. As further shown in FIGS. 8A and8B, the power radiated by antenna system 500 remains broadly anduniformly distributed around primary antenna loop 510 and secondaryantenna loops 530 at the surface of the skin of subject 110.

FIG. 9 is a flow diagram of an example process 900 for providingwireless power to a device implanted in a body of an individual, inaccordance with an embodiment of the present disclosure. Example process900 may be implemented using antenna system 500 and the other variousfeatures and aspects disclosed herein. As illustrated in FIG. 9, at step910, a first electromagnetic wave is produced. For example, a firstantenna loop, such as primary antenna loop 510, may be controlled toproduce a first electromagnetic wave. At step 920, a secondelectromagnetic wave is produced. For example, at least one of thesecondary antenna loops 530 may be controlled to produce a secondelectromagnetic wave. Then, at step 930, an interference pattern isgenerated by interfering the first and second electromagnetic wave. Theinterference pattern may include interference maxima located at orsubstantially close to an implanted device (such as implanted device120) in the body of the individual. As disclosed herein, antennacontroller 136 may be configure to control one or more properties of theantenna loop(s) to adjust the interference pattern caused the first andsecond electromagnetic waves to interfering with one another. Also, insome embodiments, alignment may be performed, during operation, so thatthe interference maxima of the interference pattern is at orsubstantially close to the implanted device in the body of theindividual.

As part of step 930, antenna controller 136 may control a property ofthe first antenna loop (e.g., primary antenna loop 510) so as tomaintain the location of the one of the interference maxima at orsubstantially close to implanted device 120. In some embodiments, thecontrolled property of the first antenna loop may include a reactance ofa reactive element associated with the first antenna loop. For example,the reactive element may be one of a variable capacitor or a variableinductor. Also, in some embodiments, the controlled property of thefirst antenna loop may include a loading capacitance or a loadinginductance.

As part of step 930 or another step in process 900, antenna controller136 may control a property of a signal for the first antenna loop so asto maintain the location of the one of the interference maxima at orsubstantially close to the implanted device 120. In some embodiments,the property of the signal includes at least one of a frequency, phase,or magnitude of the signal. Also, in some embodiments, a maximum powerat a skin of the body of the individual caused by at least one of thefirst electromagnetic wave or the second electromagnetic wave may beless than a power at the one of interference maxima. Further, in someembodiments, a maximum SAR caused by at least one of the firstelectromagnetic wave or the second electromagnetic wave may be below orequal to 1.6 watts per kilogram.

In the preceding specification, various exemplary embodiments andfeatures have been described with reference to the accompanyingdrawings. It will, however, be evident that various modifications andchanges may be made thereto, and additional embodiments and features maybe implemented, without departing from the broader scope of theinvention as set forth in the claims that follow. For example,advantageous results still could be if components in the disclosedsystems were combined in a different manner and/or replaced orsupplemented by other components. Other implementations are also withinthe scope of the following exemplary claims. The specification anddrawings are accordingly to be regarded in an illustrative rather thanrestrictive sense. Moreover, it is intended that the disclosedembodiments and examples be considered as exemplary only, with a truescope of the present disclosure being indicated by the following claimsand their equivalents.

What is claimed is:
 1. A power system for providing wireless power to adevice implanted in a body of an individual, comprising: a first antennaloop that produces a first electromagnetic wave; and at least one secondantenna loop that produces a second electromagnetic wave, the first andsecond antenna loops positioned to generate electromagnetic waves thatwill interfere with one another to produce an interference patternincluding interference maxima, wherein a location of at least one of theinterference maxima is configured to be located at or substantiallyclose to a depth of the device implanted in the body of the individual.2. The power system of claim 1, further comprising an antenna controllerconfigured to control a property of the first antenna loop in order tomaintain the location of at least one of the interference maxima at orsubstantially close the depth of to the device implanted in the body ofthe individual.
 3. The power system of claim 2, wherein the controlledproperty of the first antenna loop includes a reactance of a reactiveelement associated with the first antenna loop.
 4. The power system ofclaim 3, wherein the reactive element is one of a variable capacitor ora variable inductor.
 5. The power system of claim 2, wherein thecontrolled property of the first antenna loop includes a loadingcapacitance or a loading inductance.
 6. The power system of claim 1,further comprising an antenna controller configured to control aproperty of a signal for the first antenna loop in order to maintain thelocation of at least one of the interference maxima at or substantiallyclose to the depth of the device implanted in the body of theindividual.
 7. The power system of claim 6, wherein the controlledproperty of the signal includes at least one of a frequency, phase, ormagnitude of the signal.
 8. The power system of claim 6, wherein theantenna controller includes a tunable phase shifter.
 9. The power systemof claim 1, wherein a maximum power at a skin of the body of theindividual caused by at least one of the first electromagnetic wave orthe second electromagnetic wave is configured to be less than a powerassociated with at least one of interference maxima.
 10. The powersystem of claim 1, wherein a maximum specific absorption rate (SAR)caused by at least one of the first electromagnetic wave or the secondelectromagnetic wave is below or equal to 1.6 watts per kilogram.
 11. Amethod for providing wireless power to a device implanted in a body ofan individual, comprising: producing, by a first antenna loop, a firstelectromagnetic wave; producing, by at least one second antenna loop, asecond electromagnetic wave, the first and second electromagnetic wavesinterfering with one another to produce an interference patternincluding interference maxima, wherein a location of at least one of theinterference maxima is at or substantially close to the device implantedin the body of the individual.
 12. The method of claim 11, furthercomprising: controlling, using an antenna controller, a property of thefirst antenna loop so as to maintain the location of at least one of theinterference maxima at or substantially close to the device implanted inthe body of the individual.
 13. The method of claim 12, wherein thecontrolled property of the first antenna loop includes a reactance of areactive element associated with the first antenna loop.
 14. The methodof claim 13, wherein the reactive element is one of a variable capacitoror a variable inductor.
 15. The method of claim 12, wherein thecontrolled property of the first antenna loop includes a loadingcapacitance or a loading inductance.
 16. The method of claim 11, furthercomprising: controlling, using an antenna controller, a property of asignal for the first antenna loop so as to maintain the location of atleast one of the interference maxima at or substantially close to thedevice implanted in the body of the individual.
 17. The method of claim16, wherein the controlled property of the signal includes at least oneof a frequency, phase, or magnitude of the signal.
 18. The method ofclaim 12, wherein a maximum power at a skin of the body of theindividual caused by at least one of the first electromagnetic wave orthe second electromagnetic wave is less than a power associated with atleast one of interference maxima.
 19. The method of claim 12, wherein amaximum specific absorption rate (SAR) caused by at least one of thefirst electromagnetic wave or the second electromagnetic wave is belowor equal to 1.6 watts per kilogram.
 20. A system for providing power toa device, comprising: a first antenna loop; a power source configured toprovide power to the first antenna loop and cause the first antenna loopto produce a first electromagnetic wave; a plurality of second antennaloops configured to absorb a portion of the first electromagnetic waveand produce second electromagnetic waves, the first and secondelectromagnetic waves interfering with one another to produceinterference maxima; and an antenna controller coupled to the firstantenna loop, the antenna controller being configured to control aproperty of the first antenna loop so as to maintain the location of atleast one of the interference maxima at or substantially close to adepth of the device implanted in the body of the individual.